Nodes are defined as intelligent data terminal equipment (DTE), such as terminals, PCs, work-stations, computers, and servers. Nodes can transmit and receive communications signals. A network is defined as a group of nodes joined together by a communications medium for transporting the communications signals. In a network context, nodes are sometimes referred to as end-stations. An end-station generally does not have the capability to expand the network.
One type of network is a token ring. Usually, a token ring is assumed to be a baseband ring specified by the "Token Ring Access Method and Physical Layer Specification," ANSI/IEEE 802.5-1992 (ISI DP 8802/5) standard, hereinafter the "802.5 standard". However, token rings can be applied to a number of different network topologies and access methods.
Although token rings can come in any number of physical and logical arrangements, token rings generally include a closed loop or main ring, generally known as backbone or trunk circuit (trunk), made of a one or more ring segments of the communications medium. The medium may be conductive wires configured as, for example, twisted pairs, co-axial cable, or fiber optical cable, micro-wave links, and the like.
In order to facilitate the construction of ring networks, secondary, or internal rings may be provided. Typically, a wiring concentrator or Multi-station Access Unit (MAU) provides for the connection of several nodes at a single trunk location, or wiring center, for example a communications closet in an office building. The nodes of a network are connected to the MAU via tertiary rings circuits usually known as lobe circuits (lobes). In other words, lobes provide the communications link between nodes and MAUs, and the ring segments of the trunk are the communications link which connects MAUs.
A MAU usually includes a plurality of ports for physically connecting the lobe cables. A Ring In (RI) port and a Ring Out (RO) port are also provided for connecting to the ring segments of the trunk. Connections between the lobes and the trunk inside the MAU are usually provided by means of a trunk coupling units (TCU).
It is a problem to arrange the configuration of the network without disrupting the operation of the network. The prior art has provided various devices for constructing a network, however, they are generally difficult to adjust in number or location once the network is installed in a physical environment such as an office building.
It is a problem to establish and maintain appropriate data signaling frequencies or "speeds" on the communications network. In known ring networks, information may be communicated among the nodes at varying frequencies or speeds, for example 4, or 16 megabytes per second (Mb/sec). It is a problem to initially establish an optimal signaling speed on the network as the network is activated, for example, during power-up, or after a network failure. Also, once a ring becomes operational, it is a problem to maintain the optimal signaling speed as the network is re-arranged, or when dormant components start communicating on the network.
Prior art networks typically require operator intervention to establish an initial signaling speed on the network. And, in most prior art networks, attempts to insert components, such as MAUs, which are configured to communicate at different frequencies or speeds will generally cause the network to crash.